Current perspectives on the biological properties and disease implications of cystatin SN (CST1)

Cystatin SN ( CST1 ), a key cysteine protease inhibitor, has attracted significant interest for its diverse roles in disease pathogenesis. This comprehensive review examines the molecular structure and biological functions of cystatin SN, with emphasis on its mechanisms in tumorigenesis, type 2 inflammatory airway diseases, and related pathologies. Cystatin SN reportedly modulates critical processes such as cellular senescence, epithelial-mesenchymal transition (EMT), tumor microenvironment dynamics, ferroptosis, and glucose metabolism through signaling pathways including MEK/ERK, PI3K/AKT, and Wnt. The present review synthesizes current preclinical and clinical evidence on cystatin SN as a candidate biomarker and exploratory therapeutic target, highlighting that clinical translation remains in early investigative stages and requires prospective multi-center validation with standardized assays. Overall, this review consolidates current knowledge of cystatin SN biology, identifies critical gaps, and outlines priorities to guide future translational research.